没有可访问的'New'接受这个数量的参数 - 错误

Question

I have this chunk of code

Dim _timer As System.Threading.Timer

Public Sub RunTimer2()
    _timer = New System.Threading.Timer(onSave(), 
                         Nothing, 
                         TimeSpan.FromSeconds(5),     
                         TimeSpan.FromSeconds(5))
End Sub

and I get error Overload resolution failed because no accessible 'New' accepts this number of arguments. for the line where I am trying to create the timer. Although I can see in the documentation in msdn and in the libraries that it has those 4 possible types parameters that I use. I don't get it...

Answer 1

You are not passing a delegate to the onSave function. You are calling the onSave function and passing it's return value to the Timer constructor. You need to create the delegate to the function and pass that, like this:

Dim _timer As System.Threading.Timer

Public Sub RunTimer2()
    _timer = New System.Threading.Timer(New TimerCallback(AddressOf onSave), 
                         Nothing, 
                         TimeSpan.FromSeconds(5),     
                         TimeSpan.FromSeconds(5))
End Sub

Or, VB will automatically figure out the delegate type for you if you just do this:

Dim _timer As System.Threading.Timer

Public Sub RunTimer2()
    _timer = New System.Threading.Timer(AddressOf onSave, 
                         Nothing, 
                         TimeSpan.FromSeconds(5),     
                         TimeSpan.FromSeconds(5))
End Sub

Answer 2

To declare a timer in vb.net you can:

  Private MyTimer As System.Threading.Timer

  MyTimer = New System.Threading.Timer(AddressOf MyTimer_Tick, Nothing, RunEveryNMinutes * 60000, RunEveryNMinutes * 60000)

Private Sub MyTimer_Tick(ByVal state As Object)
    WriteEventLog("Timertick")

End Sub

Answer 3

That starts the timer after 5 seconds and calls it every 5 seconds

Private timer As System.Threading.Timer = New System.Threading.Timer(AddressOf DoWhatever, Nothing, New TimeSpan(0, 0, 5, 0), New TimeSpan(0, 0, 5, 0))

Private Sub dowhatever(sender As Object, e As Timers.ElapsedEventArgs)
   ' Do stuff
End Sub